Applicability of both $J^*$-integral and stress intensity factors to an interfacial crack lying along the interface between a thin film and a substrate is investigated under a thermal load of constant temperature on the surface of the thin film. Both the thin film and the substrate are assumed to be homogeneous, isotropic and elastic, and the material peoperties of them are assumed to be independent of temperature.
The transient temperature distribution due to the thermal load is calculated by a finite difference method in advance, then the stress and the strain are determined by a finite element method which in turn gives the stress intensity factor. the results are obtained as follows :
(1) the $J^*$-integral numerically evaluated is almost path independent
(2) the stress field near a crack tip is mainly of mode II.
